Isoolefin recovery



F. T. SHERK IsooLEFIN RECOVERY Jan. 24, 1967 2 Sheets-Sheet l Filed Oct. 18, 1963 Jan. 24, 1967 F. T. SHE'RK 3,300,539

I SOOLEFIN RECOVERY Filed oct. 18, 1963 Y' 2 sheets-sheet 2 O D r\ :D fm1 M l 3V Kv m i Lnl 2- o C): o u 0 j@ D y 3 lu fg Sl INVENTOR.

F,T. SHERK A TTOIQNEVS Patented Jan. 24, 196i 3,300,539 ISOOLEFIN RECOVERY Fred T. Slierk, Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware Filed Oct. 18,' 1963, Ser. No. 317,873

f 6 Claims. (Cl. 260-677) This application is a continuation-in-part of my co- -pending `application Serial No. 72,719, filed November 30, 1960, now abandoned.

This invention relates to the recovery of isoolefins from a mixed olefin stream;` In another aspect this invention relates to the recovery ofA at least two separate branch chain olefin components from corresponding streams of mixed olefins utilizing an absorbent having an affinity for branch chain olefins which increases as the molecular weight of the olefin decreases, performing a first absorption to recover a first isoolefin from a first stream of mixed olefins and subsequently using the rich absorbent thus obtained to recover the second isoolen from a second stream of mixed olefins, the second isoolefin having a lower molecular weight than the first. In another aspect this invention relates to an apparatus for performing such a plural stage absorption.

Generally speaking, solvent extraction operations are well known inthe art. `In a liquid-liquid extraction, for example, the material to be extracted, having at least two components, is contacted with a solvent in the solvent extraction zone. There are removed from the zone a raffinate portion having a relatively high proportion of the component or components for which the solvent 1has a lesser affinity and an extract phase which contains the major portion of the solvent and the component for which the solvent has the :greater afiinity. The extract phase then must be separa-ted into a lean solvent portion and a portion containing the component removed by the solvent, often by a stripping operation. I found that, by using as the extraction medium a material for which the selectivity is affected by the molecular weight of the component for which thernedium is selective, I can perform more than one separation while requiring only a single stripping operation. Thus, using a material, for example, which is selective for branch chain olefins in preference to straight chain olefins but which is selective for the lower molecular weight of two branch chain olefins', a series of separations of branch chain from straight chain olefins can Ibe made using a single stripping operation.

An object of this invention is to provide an improved solvent extraction operation. Another object of this invention is to increase the efficiency of a solvent extraction operation by reducing the relative amount of stripping necessary as compared with the separation accomplished. A further object of the invention is to provide an improved solvent extraction operation in which a plurality of separations of branch chain olefins from straight chain olefins are made with a single stripp-ing operation.

`Other aspects, objects and advantages of the invention are apparent from the specification, the drawing and appended claims.

According to my invention there are provided a process and app-aratus comprising a solvent extraction system in which a plurality of separations of branch chain olefins from straight chain olefins are accomplished with a single stripping step `by separating first a relatively high molecular weight branch chain olefin from a corresponding straight chain olefin and subsequently 'using the extract phase as the solvent feed to the solvent extraction zone wherein the relatively low molecular weight branch chain olefin is separated from its corresponding straight chain olefin, the lower molecular weight isoolefin causing the heavier molecular weight isoolefin to be separated as raffinate phase from the latter separation. Also, accord ing to my invention sulfuric acid is used to extract iso amylene from a mixture of mixed amylenes and the ex tract phase subsequently used to extract isobutylene fron mixed butylenes, the raffinate ofthe latter separation com prising butylene and isoamylenes. Further according tl my invention sulfuric acid can be used. to extract branc.` chain hexenes from straight chain hexenes, the rich acir used to extract branch chain amylenes from straight chai] amylenes, the branch chain hexenes being removed witl the straight chain amylenes, following which. the ricl acid is used to extract isobutylene from straight chain bu tylenes, the branch chain amylenes being removed as a raf finate with t-he straight chain butylenes, the two separat raffinate phases fractionated to separate respectively th butylene from the isoamylene and the amylene from thi isohexenes, the isobutylene-rich acids stripped to produc an isobutylene product and the lean acid returned to th` first mentioned solvent extraction step. My invention therefore, finds particular utility in extracting two or mori of the Igroup consisting of isobutylene, branch chain amyl enes, and branch chain hexenes from the corres'pondin,` straight chain components by solvent extraction with s-ul furie acid, wherein only a single stripping step is required When it is determined which components are to lbe ex tracted, the system is arranged so that the higher mo lecular weight combined stream is contacted with thi lean acid, the next lower molecular weight combiner stream is contacted with the rich acid from the preceding step, etc. lThat is, for example, in extracting branch chair hexenes from straight chain hexenes in a combined op eration wherein isobutylene is extracted from the straigh chain butylenes, the lean acid is first contacted with thc mixed hexene stream following which thev acid containing branch chain hexenes is contacted with the mixed butylent stream.

Whether the rst contacting step ishexenes or amylenes the contact normally is made in a temperature range of2( to F. Preferably the step is made in the range of 4:' to 65 F., more preferably in the range of 50 to 60 F.

The temperature range for absorption with an isoolefinrich acid, for displacement of the absorbed isoolefin witl a lower molecular weight isoolefin, in accordance witt my invention, broadly is the temperature range for absorption of the lower molecular weight compound witt a lean acid. For example, the broad range of operatief for a contactor wherein isobutylene is extracted frorr a mixed b-utylene stream with sulfuric acid containing z higher molecular weight branch chain olen is broadly the temperature range for extraction of isobutylene witl lean sulfuric acid. Proper operation of a contactoi wherein one branch chain olefin is displaced by another lower molecular weight branch chain olefin is obtainec by control of the temperature in accordance with othel conditions existing, including the relative concentration: of the branch chain olefins in question and the amountf of the feed streams. For example, in a system involving isoamylene and isobutylene, if it is desired to remove substantially all of the isoamylene from the sulfuric acic stream, a relatively high temperature is utilized, thu: driving substantially all of the isoamylene and a rela tively small portion of the isobutylene to the hydrocarbon phase. On the other hand, if maximum isobutylene recovery is the determining factor, a somewhat lowei temperature is used, in which case a larger portion of the isobutylene remains in the acid phase, but this phase alsc includes an appreciable amount of isoamylene. The sulfuric acid has a preference for absorption of the lowei molecular weight branch chain olens at all temperatures i the operating temperature for a particular step being :hosen in accordanccwith the above-noted criteria within he broad limits. The lower limit is determined by coniderations of ease of mixing and contacting, considering he viscosity of the acid, and the upper limit is limited `by l consideration of undesired reactions, particularly polymfrization. Therefore, neither of these limits defines an tbsolute value on one side of which the system is cornrletely inoperative while being 100 percent effective on he other side. Rather, there is a shading into undesira- )le conditions and the exact operating temperatures must )e determined by an over-al1 balance of the factors af- 'ecting the operation. In general, all of the contacting teps are carried out within the range of 20 to 100 F. )ften the extraction of a lower molecular weight branch :hain olen is made at a higher temperature than the )receding step for a higher molecular Weight branch chain ilefin, but this is not essential.

Normally the concentration of the sulfuric acid is in the ange of 40 to 75 percent by weight. When a steam tripping step is utilized for removing the final absorbed naterial from the acid, vusually the concentration is in he range of about 60 to 70 weight percent, more often lbout 65 weight percent. Steam stripping necessitates lcid reconcentration. Higher acid concentration pernits circulation of smaller amounts of acid. Higher con- :entrations are feasible because steam stripping readily emoves even the most difiicultly stripped material, isobu ylene. Acid concentration within this range also is suiti-ble for systems not involving isobutylene, even where lydrocarbon strippingis utilized since isoamylenes and )ranch chain hexenes can readily be removed even from vcids of this concentration. However, when using hydro- :arbon stripping in al system including an extraction of sobutylenes, acid of lower concentration, in the range of L to 60 Weight percent, usually 50 to 55 percent, is used o permit easier removal of isobutylene. Therefore, in eneral, the lower portion of the acid concentration range s utilized when recovering isobutylene with a' `hydroarbon stripping step whereas the upper portion'of the ange Ais utilized whenever steam 'stripping is used, so that nore economical use of the acid can be made. Utilizing lydrocarbon stripping in a system not involving isobutylne permits wider economical variation of acid concenration. r

The extraction system according to my invention is ubstantially insensitive to pressure variations, but should le operated at a pressure so that the various components ,re maintained in liquid phase. InY general, the pressure s in the range of 0 to^200 p.s.i.g. Often, the selection f an exact pressure is made on the basis of consideraions other than the efficiency of the absorption step :er se. For example, pressures can be selected to reduce he number of pumps required.

In the drawing, FIGURE 1 is a diagrammatic ow heet of one embodiment of the invention in which two eparations are made with a single stripping operation.

FIGURE 2 is a similar representation of a system in vhich three separations are made. i

FIGURE 3 is a schematic representation of the invenion applied to two lplural stage solvent extraction steps.

In FIGURE 1, the first stream to be separated is fed hrough feed conduit into contactor 11 in which lean olvent also is fed through inlet 12. A raiinate stream s removed through conduit 13 and the rich solvent hrough conduit 14 which also serves as the solvent feed 'or a second contactor 15. Into this contactor a separate nixed stream is fed through conduit 16, this stream havng a component for which the solvent is more selective han it is for the component removed in contactor 11. thus, the raffinate removed through conduit 17 from :ontactor will contain the dissolved product from the irst extraction and the component of the second mixed `.tream for which the solvent is less selective while the 'ioh solvent is removed through conduit 18 along with he product extracted from the second stream. This lati ter material is stripped from the solvent in stripper 19 and removed through conduit 20 while the lean solvent is returned through line 2l to contactor inlet 12 as shown. A fractionator 17A divides the stream in conduit 17. The first and second mixed streams are obtained from a feed splitting step as shown, the first stream fed through line 10 being the'bottoms and the second stream through line 16 being the overhead of the splitting step.

The stream 20 can be further separated in a fractionator 20A into an overhead product comprising substantially pure product from the second contactor and a bottoms comprising undesired components entrained with the above-mentioned product. This stream is transferred to a further separation step -along with the bottoms from fractionator 17A. The overhead from this fractionator contains the product which was dissolved in contactor 11 while impurities are removed in the bottoms.

.In FIGURE 2, there are three separate separations made with a single stripping step. A first mixed st-ream enters through conduit 22 into the tirst contactor 23 and is contacted there with a solvent which enters through conduit 24. Rafnate is removed through conduit 26 while the rich solvent ows through conduit 25 where it enters a second contactor 27 as the solvent for a more readily absorbed component from the second mixed stream which enters through conduit 28. Rainate is removed through conduit 29 and the solvent now rich in the component removed from the second mixed stream flows through conduit 30 to enter a third contactor 31 and to act as the solvent forl a` still more readily absorbed component in a third mixed stream entering through conduit 32. The rainate from thethird contactor is withdrawn through conduit 33 while the rich solvent flows through conduit 34 to stripper 35. Lean solvent fiows from stripper 35 through conduit 36 where it joins fresh solventin conduit 24 while the product removed from the solvent in stripper 35 is discharged through conduit 37. The raffinate from second contactor 27 is taken to a rst fractionator 37 and the raffinate from the third conduit is taken to a second fractionator 38. In each of these 'fractionators a separation is made between the component of the .raffinate which came from theearlier mixed stream and the component from the stream which entered first in thecorresponding contactor. That is, the component which was associated with the solvent as it left the iirst contactor will appear in the raiiinate from the second coni tactor along with the non-absorbed material from `the second stream. The component from the second stream which is removed by the richnsolvent from the second contactor appears in the .raffinate from the third contactor along with the non-absorbed material from the third stream. Y

Two or more stages can be countercurrently used for each step of the operation. When this is done in a step wherein one isoolen is `displacing another, the rich acid from the preceding step is fed into theY contacting step for the semi-lean hydrocarbon stream ofthe plural stage step. This results in more complete removal of the isoolen in the rich acid `from the preceding step as we'll as'. more complete extraction of the lighter isoolefin in the acid phase.

In FIGURE 3 there is illustrated a combination ofl process equipment adapted for processing a stream containing more than one component to be separated, and utilizing plural stage operation. The combined stream enters a first fractionator through inlet conduit 51. The bottom product from fractionat-or 50 is fed to a second fractionator 52 through feed line 53. The overhead product from fractionator 52 is processed through an accumulator 54 and a series of contacting vessels 58, 59 and 6), having associated with these vessels respectively settling vessels55, 56 and 57. Other1 types of contacting means can be used in place of vessels 53, 59 and 60, as for example, a pump and pipe loop or other type of mixing conduit. The -lean absorbent is fed through conduit 61. Rich absorbent from vessel 57 is lreturned as lean absorbent to vessel 59 through conduit 62 while the rich absorbent from vessel 56 is returned to vessel 58 as lean absorbent through conduit 63; The rich absorbent from vessel 55 is fed to the system for treating the overhead from fractionator 50 through cond-uit 64. The raffinate from'vessel 57 is withdrawn through conduit 72.

The accumulator 65 and contacting vessels 69, 70 and 71 and their associated settling vessels 66, 67 and 68are connected as shown in a manner similar to the system of vessels 58, 59 and 60. The raffinate from vessel 68 is conducted to a fractionato-r 73 and the extract from vessel 66 is taken to stripper 74. Lean absorbent from stripper 74 can be returned to conduit 61. The overhead from stripper 74 is taken to a fractionator 80, the overhead from fractilonator 80 being the desired product from the solvent extraction of the step which comprises vessels 66, 67 and 68, while the bottoms containing undesired extracted material are combined with the bottoms from fractionator 73 and taken to a `fractionator 81 from which the overhead contains the extracted material from the step which comprises vessels 55, 56 and 57, while the bottom stream contains impurities.

Example I butylenes and the branch chain amylenes while the stream removed through conduit 18 comprises the acid with the branch chain butylenes. In stripper 19, the branch chain butylenes are separated from the acid, the butylenes being removed through conduit 20 4and the acid returned through line 21 to unit 12.

In the following table the feed stream results from a separation of a catalytically cracked product strearm. The temperature in contactor 11 is 40 F., and the temperature in contacter 15 is 80 F. The composition of theI various streams is given in this table. The pressure is approximately 175 p.s.i.a. in both contacting steps.

branch chain hexencs and the acid are removed througl line 25 and then to vessel 27. The temperature in con CII tactor 2,7 is F. The second mixed stream which en tersthrough conduit 28 comprises mixed amylenes and th( ranate removed through 29 comprises branch chail hexenes and straight chain amylenes, and the stream re moved through conduit 30 comprises the acid and th( branch chain amylenes. The temperature in contactor 31 is 60 F. With a third mixed stream comprising mixe( butylenes owing through conduit 32, the stream in con duit 33 comprises the branch chain amylenes and th( straight chain butylenes, the branch chain butylenes bein; removed through conduit 34 with the acid. In strippe- 35, the branch chain butylenes are removed through con duit37and the lean acid returned through conduit 36 In fractionator 37, the :branch chain hexenes are separate( from the straight chain amylenes while in the fractionato 3-8 the branch chain amylenes are separated from th( straight chain butylenes. The pressure in contactors 23 27 and 31 is approximately 175 p.s.i.a.

Example III As. an example of the operation according to FIGURE 3 a mixed stream of catalytically cracked gasoline is fe( through conduit 51 to fractionator 50. In fractionato. S0 a vbutylene stream is taken overhead and the heavie material is taken through conduit 53 to fractionator 52 Here an amylene stream is taken overhead and the heavie` material removed at the bottom. Lean sulfuric aci( enters through conduit 61. From accumulator 54 th( mixed amylenes pass through vessels 55, 56 and 57, he coming progressively leaner in branch chain amylenes an( thus relatively richer in straight chain amylenes until z relatively ypure straight chain amylene stream is remove( as ranate through conduit 72. The temperature ir vessel 57 is 40 F. and the temperature in vessels 55 an( 56 is 60 F. The lean acid becomes progressively riche in branch chain amylenes as it progresses from vessel 5. to vessel 56 to vessel 55 and a stream is removed througl conduit 64 which is rich in branch chain amylenes and i: fed to the butylene separation system. The stream whicl Hows from accumulator 65 is predominantly mixed butyl enes and becomes progressively leaner in branch chair butylenes and richer in branch chain amylenes, entering from line 64, as it progresses through vessels 66, 67 an( 68. The temperature in vessel 68 is 40 F., in vessel 6A MATERIAL'BLANCE, MOLS PER HOUR- trans-butene-Z cisbutene2 3-methy1butene Isopentane. Pantone-1 2-methylbutene-1. N -pentane 27 trans-pentene-2 Total 1, 055

1 Basis is the mols of monomer. 2 100% concentration.

Example II In an example of the operation according to FIGURE 2, the temperature in contactor 23 is 60 F. The first stream which is introduced through conduit 22 comprises mixed hexenes, and the stream entering through 24 is sulfurie acid, in which case the ranate -removed through line 26 comprises the straight chain hexenes While the is 70 F., and in vessel 66 is 90 F. The stream remove( from vessel 68 through line 75 is predominantly brancl chain amylenes and straight chain butylenes which ar( sepa-rated in fractionator 73. The stream remove( through line 76 comprises the acid together with brancl chain butylenes picked up in vessel 68 and a portion o: the branch chain amylenes which entered with the aci( irough conduit 64. The stream removed through con= DISPLACEMENT DEMONS'TRATIONT uit 77 is richer in branch chain butylenes and leaner in ROOM TEMPERATURE mylenes and the stream which 1S removed through con- Original Charge: 39.2 grains HzSiO (63.6 Weight Percent) uit 78 comprises the acid together with substantially all 9.80 grams 2MB2 f the branch chain butylenes in the system and substan- 5 ally all of the amylene has been removed. This stream Grams Weight ows through stripper 74 wherein the 'branch chain butyl- Percent ries and the lean acid are separated and the lean acid :om stripper 74 may be returned to the system through Dispiacing Liquid: enduit 61 The r s ur ll ont ct'n v l ic" 12's 'm3 P s e U1 a C a l g @55e S 15 aP 10 i0, 1&9 5g 7 roximately 175 p.s.i.a. 31 7 Example IV n Runs were made to demonstrate the selectivity of sul- 11 iric acid for lower molecular weight branch chain olens 18.9 76 3 i preference to higher molecular weight branch chain 2'@ 8-1 letins. In these runs, the hydrocarbon components were 24.78 harged to a stainless steel vessel having means for stiring containing the acid. The contents were stirred for o 28 33.0 0 minutes and then allowed to settle for 20 minutes,`after 1' 39 6" 4 fhich the hydrocarbon phase was analyzed by passing a 18.7 ample from the hydrocarbon phase in the vessel directly Y irough a chromatographic analyzer. Results are given lApproximatc. i the following table:

QUILIBRIUM TESTS FOR tensor-2 METHYLBUTENE-MsonUTYLENE ISOBUTANE, 40 F.

Charge Hydrocarbon Phase Acid Phase Grams Weight Grams Weight Grams i Weight Percent Percent y Percent 5. 64 i9. 8 3. 2i i5. 1 2. 43 33. 9 5.92 20.8 1.18 5 55 4.74 66.1 16. 9 59. 4 16.9 79 4 28.5 21.3 7.17 Weight acid used,C35.5 graris (63.6 Weight Percent H2504).

. i 4' 15.1 Select ity (1S) 2m T5 X g55-5.3.

[Room temperature (78 FJ] Charge Hydrocarbon Phase Acid Phase Grams Weight Grams Weight Grams Weight Percent Percent 1 Percent 1 1.0 inol percent unidentified in analysis, normalized out. Weight acid used, 48.0 grains (63.6 Weight Percent HzSOi). se1ectivity=30.1.

Charge Hydrocarbon Phase Acid Phase Grains Weight Grains Weight Grams Weight Percent Percent 1 Percent 5. e1 20. i 3.70 17. 6 5.53 19.8 0.50 2.4 10. 8 60. 2 i0. 8 80. o

1 4.8 inol percent unidentified in analysis, normalized out. Weight acid used, 38.8 grams (63.6 Weight Percent H2804). Se1ectivity=19.3.

This demonstrates the selectivity of sulfuric acid for This demonstrates the displacement of an isoamylene .obutylene in preference to isoainylene. from an acid phase by contact with a mixed C4 stream 70 containing isobutylene. Exam le V p v Reasonable variation and modification are possible A run was made in the same manner as the runs of within the scope of the foregoing disclosure, lthe drawing lxample IV, except that the amount of isoarnylene was and the appended claims tothe invention, the essence of dded to the acid prior to contact with the remainder of which is a process and apparatus by which a plurality of ie hydrocarbon charge. Results are given below: 75 solvent extraction steps are accomplished with a single aaoopss 9 stripping step by utilizing the variation in selectivity with molecular weight as well as variation in selectivity between products of similar molecular weight but varying structure.

I claim:

1. A process for recovering isoolefins which comprises contacting a stream containing relatively high molecular weight olefns with sulfuric acid to obtain an olen railinate and an isoolen-rich acid, contacting said isoolenrich acid with a stream containing lrelatively- "low molecular weight 'olefins separable by distillation from said high molecular weight olens to obtain a rafnate containing relatively high molecular weight isoolefins in relatively low molecular weight olen and a relatively low molecular weight isoolefin-rich acid, stripping said relatively low molecular weight isoolen-rich acid to obtain lean acid and relatively low molecular weight isoolen, separating said relatively high molecular weight isooleiin from said raffinate containing relatively high molecular weight iso- 2. A process for recovering isoolens which comprises contacting a stream containing mixed amylenes with sulfuric acid to obtain an amylene rainate and an isoamylene-rich acid, contacting said isoamylene-rich acid with a stream containing mixed lbutylenes to obtain a rainate containing butylene and isoamylene and an isoamylene-rich acid, contacting said isoamylene-rich acid to obtain lean acid and isobutylene and separating said rainate containing butylene and isoamylene to obtain butylene and isoamylenes.

3. A process for recovering isoolens which comprises contacting a stream containing mixed hcxenfes with sulfuric acid to obtain a hexene rainate and an isohexenerich acid, contacting said isohexene-rich acid with a stream -containing mixed amylenes to obtain a ranate containing amylene and isohexenes, and anisoamylene rich acid, contacting said isoamylene-rich acid with a stream containing mixed butylenes to obtain a rainate containing butylene and isoamylenes and an isobutylenerich acid, stripping said isobutylene-rich acid to obtain lean acid and isobutylene, separating said raffinate containing amylene and isohexenes to obtain amylene and isohexene 'and separating said ralinate containing butylene and isoamylenes to obtain butylene andisoamylene.

4. A process for recovering isoolefns which comprises contacting a stream containing relatively high molecular weight olens with sulfuric acid at -a temperature in the range of '20 to 120 F. to obtain an olefin ratinate and an isoolevin-rich acid, contacting said isooleln-rich acid at a temperature in the range of to 120i F. with a stream containing relatively low molecular weight olens separable by distillation from said high molecular weight olens to obtain a lraffinate containing relatively high molecular weight isoolen in relatively low molecular weight olen and a relatively low molecular weight isoolen-rich acid, stripping said relatively low molecular weight isooleIin-rich acid to obtain lean acid and relatively low molecular weight isoolen, separating said relatively high molecular weight isoolen from said rainate containing relatively high molecular weight isoolen and relatively low molecular weight olen.

5. A process for recovering isoolens which comprises contacting a stream containing mixed amylenes with sulfuric acid at a temperature in the range of 20 to 120 F. to obtain an amylene rainate and an isoamylene-rich acid, contacting said isoamylene-rich acid at a temperature in the range of 20 to 120 F. with a stream containing mixed butylenes to obtain a raffinate containing butylene and isoamylene and an isobutylene-rich acid, stripping said is-obutylene-rich acid to obtain lean acid and isobutylene and separating said `rainate containing butylene and isoamylene to obtain butylene and isoamylene.

6. A process for `recovering isoolefins which comprises contacting a stream containing mixed hexenes with sulfurie acid at a temperature in the range of 20 to 120 F. t-o obtain a hexene rainate and an is-ohexene-rich acid, contacting said isohexene-rich acid at a temperature in the range of 20 to 120 F. with a stream containing mixed amylenes to obtain a rainatecontaining amylene and isohexene, and an isoamylene-rich acid, contacting said isoamylene-rich acid at a temperature in the range of 20 to F. with a stream containing mixed butylenes to obtain a rafnate containing butylene and isoamylenes and an isobutylene-rich acid, stripping said isobutylene-rich acid to obtain lean acid and isobutylene, sepa-rating said rainate containing amylene and isohexene to obtain amylene and isohexene and separating said ranate containing butylene and isoamylenes to obtain butylene and isoamylene.

References Cited by the Examiner UNITED STATES PATENTS 1,281,497 12/1961 Cahn et al. 260-677 3,113,163 12/1963 Edwards et al. 260-677 FOREIGN PATENTS 908,077 10/ 1962 Great Britain.

ALPHONSO D. SULLIVAN, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Noc 3, 300, 539 January Z4, 1967 Fred Ta Sherk It is hereby certified that error appears in the above numbered petent requiring correction and that the said Letters Patent should read as corrected below.

Column 9, line 19, strike out "iso" and insert instead isoolefin and relatively low molecular weight olefin. line 26, strike out "isoamylene", each occurrence, and insert instead isobutylene same line 26, for "contacting" Signed and sealed this 10th day of October 1967.

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents Edward M. F l'etcher, Ir.

Attestng Officer 

1. A PROCESS FOR RECOVERING ISOOLEFINS WHICH COMPRISES CONTACTING A STREAM CONTAINING RELATIVELY HIGH MOLECULAR WEIGHT OLEFINS WITH SULFURIC ACID TO OBTAIN AN OLEFIN RAFFINATE AND AN ISOOLEFIN-RICH ACID, CONTACTING SAID ISOOLEFINRICH ACID WITH A STREAM CONTAINING RELATIVELY LOW MOLECULAR WEIGHT OLEFINS SEPARABLE BY DISTILLATION FROM SAID HIGH MOLECULAR WEIGHT OLEFINS TO OBTAIN A RAFFINATE CONTAINING RELATIVELY HIGH MOLECULAR WEIGHT ISOOLEFINS IN RELATIVELY LOW MOLECULAR WEIGHT OLEFIN, AND A RELATIVELY LOW MOLECULAR WEIGHT ISOOLEFIN-RICH ACID, STRIPPING SAID RELATIVELY LOW MOLECULAR WEIGHT ISOOLEFIN-RICH ACID TO OBTAIN LEAN ACID AND RELATIVELY LOW MOLECULAR WEIGHT ISOOLEFIN, SEPARATING SAID RELATIVELY HIGH MOLECULAR WEIGHT ISOOLEFIN FROM SAID RAFFINATE CONTAINING RELATIVELY HIGH MOLECULAR WEIGHT ISOOLEFIN AND RELATIVELY LOW MOLECULAR WEIGHT OLEFIN. 